Method for inhibiting corrosion of metal using polysulfone compounds

ABSTRACT

A metal corrosion inhibitor consisting of a polysulfone compound obtained by copolymerizing or interpolymerizing sulfur dioxide and at least one 1,6-diene compound. The above metal corrosion inhibitor may be added in a corrosion-inhibitorily effective amount, preferably at least 1 ppm., to a corrosive medium, with which a metal comes into contact, to inhibit the medium from corroding the metal.

United States Patent [191 Harada et al.

METHOD FOR INHIBITING CORROSION OF METAL USING POLYSULFONE COMPOUNDS Inventors: Susumu Harad'a; Masami Haruta;

Tadashi Kato, all of Koriyama, Japan Nitto Boseki Ct, Ltd., Fukushima, Japan Filed: Jan. 24, 1973 I Appl, NO.I 326,290

Assignee:

Foreign Application Priority Data July 26, 1972 Japan 47 74747 References Cited UNITED STATES PATENTS 6/1956 Gerhardt et al. 252/391 Nov. 18, 1975 2,938,034 5/1960 Cislak 252/149 2,938,907 5/1960 Rainey et al., 252/391 3,121,091 2/1964 Green 21/2.7 R 3,414,521 12/1968 Teumac 21/17 3,502,578 3/1970 Raifanider Ill/2.5 R UX 3,585,118 6/1971 Harada et al. 260/793 A 3,669,612 6/1972 Annand et al. 21/27 R 3,730,901 5/1973 Knox et a] 3,809,655 5/1974 Williams 252/391 Primary Examiner-Barry S. Richman Assistant Examiner-Bradley R. Garris Attorney, Agent, or FirmKarl W. Flocks [57] ABSTRACT A metal corrosion inhibitor consisting of a polysulfone compound obtained by copolymerizing or interpolymerizing sulfur dioxide and at least one 1,6-diene compound. The above metal corrosion inhibitor may be added in a corrosion-inhibitorily effective amount, preferably at least 1 ppm., to a corrosive medium, with which a metal comes into contact, to inhibit the medium from corroding the metal.

6 Claims, No Drawings LMETHOD FOR INHIQBITING connosiou F METAL USINGPOLYSULFONE COMPOUNDS This invention relates to a corrosion inhibitor 'for metals in water, aqueous solutions of salts or aqueous solutions of inorganic or organicacids, and to a method for inhibiting the corrosion of the metals with said inhibitor.

Corrosion of steel members in various coolers due to the oxygen or carbon dioxide dissolved in cooling water in recycle systems has resulted in severe troubles. Various methods have been proposed for the inhibition of such corrosion.

Various corrosion inhibitors have also been proposed for inhibiting the corrosion of metals caused by acid solutions used in the cleaning of metal surfaces, which is carried out for the removal of scales which stick to inner parts of an evaporator or boiler or for the pretreatment of platings.

Furthermore, various inhibitors have been proposed for decreasing the loss of steel, reducing the amount of acid required and obtaining beautiful finished surface in pickling metals, especially, steel.

This invention provides a metal corrosion inhibitor represented by the general formula: v

l/l t l LW. l.

wherein M is at least one member selected from the.

group consisting of 3 5 CH2 (IIH C|HCHZ (l) CH, CH,

in which-R 'and R which be the same'or' different,

are hydrogen, straight or branched chainalkyl's'having 1 to l8'carbon atoms, aryls having 6 to 24 carbon atoms, aralkyls having 710 25 carbon atomsfcarboxymethyl, carboxyethyl, cyanomethyl, 2 cyanoethyl, 2- sulfoethyl, sulfopropyl, 2-hydroxyethyl, 3-chloro-2- hydroxypropyl, ally], propargyl or a or ,B-napli- .thomethyl; and X is Cl, Br, I, CH COO, H PO i in which Y is CH or O; and X is the same as defined regarding formula (1),

in which R is hydrogen, a straight or branched chain alkyl having 1 to 12 carbon atoms, hydroxymethyl, 2- hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, NH chloromethyl or a group represented by formula (III- A):

CH N R (Ill-A) in which R,, R and R which may be the same or different, are hydrogen, straight or branched chain alkyls having 1 to 12 carbon atoms, aralkyls having 7 to 9 carbon atoms or Z-hydroxyethyl, including the case where and the case where means r N3, NQ, NQ or NQ 5 COOH CONHZ and X is the same as defined regarding the formula (I),

or by formula (lll-B):

(Ill-B) in which R,, is hydrogen, a straight or branched chain alkyl having 1 to 18 carbon atoms, an aralkyl having 7 to carbon atoms, 2-hydroxyethyl, allyl or propargyl; and X is the same as defined regarding the formula (1),

-CH cHcH, and

2 (VII) (VIII) tive amount of said metal corrosion inhibitor to a corrosive medium with which the metal contacts.

The metal corrosion inhibitor of this invention is a polysulfone obtained by copolymerizing or interpolymerizing sulfur dioxide and at least one compound selected from the group consisting of compounds represented by the following formulas (A) (H):

(G) and The compounds represented by the general formulas (A) to (H) are all 1,6-diene type unsaturated compounds and generally, these are easily copolymerized with sulfur dioxide to produce polysulfones which are 1 z 1 cyclocopolymers. A number of these polysulfones have been disclosed by the inventors. (Refer to Japanese Pat. Publication No. 14587/66; US. Pat. No. 3,375,233 and 3,585,118; British Pat. Nos. 1,098,500 and 1,275,157; and Preprint IV at the 26th Annual Meeting of the Japan Chemical Society, P. 1820 (1972)).

For example, the copolymerization of the compounds represented by the formula (I) with sulfur dioxide results in polysulfones having the following structure:

In the present invention, it is necessary that in the polysulfone compound as the metal corrosion inhibitor, the sulfur dioxide component be contained in a molar fraction of at least 0. l. When the amount of the 'sulfur dioxide component is smaller, there is substantially no difference in corrosion-inhibiting effect between such a polysulfone compound and a polymer free from the sulfur dioxide component. In other words, in such a smaller amount of the sulfur dioxide component, there is seen substantially no enhancement of effect as corro sion inhibitor by copolymerizing sulfur dioxide. In the corrosion inhibitor of this invention, the maximum amount of the sulfur dioxide component is a molar fraction of 0.5, the preferable amount is a molar fraction of 0.3 to 0.5, and the most preferable amount is a molar fraction of 0,5. The term molar fraction used herein refers to an average value, and hence, each single molecule may contain the sulfur dioxide component in an amount outside the above-mentioned range.

In the preparation of the polysulfone compound as the corrosion inhibitor, sulfur dioxide is very easily copolymerized with at least one monomer having formulas (A) to (H) corresponding to the M component of the above general formula, and the sulfur dioxide and the above monomer or monomers are falternately bonded to each other to form an alternating copolymer as mentioned above. Where the above monomer or monomers (A) to (H) are used in excess of sulfur dioxide in the copolymerization, it is considered that an alternating copolymer or interpolymer in which the M component, i.e. the monomer or monomers, and the sulfur dioxide component are present in equimolar amounts is mainly formed, and a homopolymer or copolymer composed only of the M component based on 3 the excessive monomer or monomers is partly formed, and simultaneously, a block copolymer consisting of the block of an alternating copolymer of the M component and the sulfur dioxide component and the block of a polymer composed only of the M component is also partly formed. Accordingly, where the monomers (A) to (H) corresponding to the M component are used in excess of sulfur dioxide, the corrosion inhibitor of this invention is a mixture of these polymers. However, in general, it is very difficult to isolate each copolymer from the mixture, and hence, examples in the case of an excess of the M component will hereinafter be illustrated in the form of a mere copolymer, and molar fractions of the respective components will be indicated."

Causes of corrosion of metals in an aqueous solution vary depending upon the kind of the solution, namely, the kind of substances dissolved therein, temperature and the kind of the metals. For example, the main causes of corrosion of metals in industrial water are' considered to be the oxygen and carbon dioxide dissolved in water, and in the case of pickling solutions, corrosion is, of course, caused by acids. Effective corrosion inhibitors aredetermined depending upon the kinds of substances which cause corrosion, and even if the substances which cause corrosion are the same, effective inhibitors also vary when the temperature used is different. Furthermore, inhibitors to be added to pickling baths must meet various requirements, e.g., they should not .lower the speed'of removal of scales, they must result in a beautiful finished surface and they must have an excellent solubility and stability in the bath. In view of these requirements, the corrosion inhibitors must be tailor made.

v The polysulfone compounds used in this invention have the following general characteristics as corrosion inhibitors for metals:

1. Usually, low molecular weight compounds have been used as corrosion inhibitors, but the polysulfones used in this invention are high molecular weight compounds (corresponding to intrinsic viscosities of 0.01 to 2.0 dl/g as measured in N/lO NaCl solution at 30C). (Conventionally, some of high molecular weight compounds have been used and it has been known that the high molecular weight compounds, even when used in an extremely smaller amount than low molecular weight compounds containing the same functional groups as those of said high molecular weight compounds, can exhibit the same corrosion inhibiting effect as the low molecular weight compounds.)

2. The polysulfone compounds used in this invention include a great number of compounds which have a common basic. skeleton, but have different side chains. Moreover, any two or more compounds represented by the general formulas (I) to (V) may be copolymerized with sulfur dioxide into interpolymers, and hence, such inhibitors as having different two or more functional groups in one molecule are obtained. Therefore, suitable polysulfones may be chosen depending upon corrosion environment.

. The polysulfone compounds are exceedingly stable in acids. Therefore, the corrosion inhibiting effect can be maintained for a long period of time when the compounds are used in acids, e.g., in the pickling of steel.

The polysulfone compound of this invention per se can act as a metal corrosion inhibitor, and therefore, it is generally added alone to a corrosive medium. However, it may be added along with an anticorrosive or synergistic agent which is known in the art, such as alkali halides, low molecular weight organic amine compounds and acetylene alcohol.

The amount of the polysulfone compounds added to a corrosion bath varies depending upon the kind of the compounds and corrosion environment, but generally, they may be used in an extremely low concentration. The addition in an-amount of 1 ppm. to a corrosion bath can attain a considerable corrosion inhibiting effect, but usually they are used in a concentration higher than 5 ppm.

As mentioned before, the polysulfone compounds used in this invention include a great number of compounds, and the representatives thereof are as follows, and the corrosion inhibiting effects of thirty of these compounds will be specifically explained in the Examples given hereinafter:

CH, CH2

(Dimethyldiallylammonium chloride-S0 copolymer) \CIHCH 30 CH CH. 01 l l cl- H/ \H n [1, 0.08 dl/g CH 7 CH \CH-CH /s\ n in i (7 O/\(; 3 I ml N -Cl- CH3 CH; 11

These polysulfone compounds having the above struc- EXAMPLE tures l) to (30) can be prepared by the method already disclosed by the inventors (Sec Japanese PaL This example illustrates the effect ot the corrosion Publications No 4587/66 and Na 3 1842/7]; Us 55 inhibitors of this invention against corrosion of a mild Pat. No. 3,375,233 and 3,585,118; British Pat. Nos. 5M1 P in city wuwr- 1993500 and 1 275 57 and p [V at the 26th Standstill tests were carried out for 100 hours at Annual Meeting of the Japan Chemical Society, p. 2 lfsmg Pollshcd Steel Plate l-" (abbrevia- |820 1972) or by simflar mcth0ds However in gem tron oi Japanese Industrial Standards) G3 l4l SPCCB era], the polysulfone compounds used in this invention M 80 X 20 X 1 mm] as Panel .exllmim the CffOl-IS y have a low degree Ur polymcrimflom and those of corrosion inhibitors. The results are shown in Table having a degree of pOWmcriZation higher than 50 are l, m which the corrosion lnhibltmgrate was calculated not especially required. Therefore, the copolymerizatmm the tlllowmg mrmulill tion is usually carried out in water.

The following examples illustrate some specific em- I) r D f t Lgl'LC O COI'I'QSIQI] tgl'CL O COI'I'OSIUI bodiments 0i llilb'lnVLll UOl'l it is to beunderstood, (when mrmshm when Cmmsim however, that this invention IS in no way limlted to the inhibitor is ildtitld inhibitor is added 1: examples. Degree of corrosion when no corrosion inhibitor is added Table l Dodecyl- Corrosion Polyf trimethylsulfone v ammonium inhibitors (1) (4) (8) (l2) (l7) (I8) (21) (22) (24) 6), (29) chloride (comparative example) Concentration l l0 l0 I0 10 IO l0 It) l0 5 (ppm) Corrosion inhibitor 82.4 88.4 96.5 82 5 96.5 95 3 92.6 89.5 95.4 89.5 92.4 34.2 efficiency Test panel: Polished mild steel plate (.llS. G3l4l-SPCCB 80 X X 1 mm). Corrosive liquid: Cit water Amount of liquid: 5 cc per cm of the steel plate Treatment: At 20C for l()() hours.

EXAMPLE 2 EXAMPLE 3 The same test panel as in Example 1 was subjected to The same test panel as in Example 1 was subjected to corrosion treatment in city water under agitation at corrosion treatment in .110 hydrochloric acid at 20C about C for 100 hours. The results are shown in for 100 hours. The results are shown in Table 3.

Table 2.

Table 2 Dodecyltrimethyl Corrosion Polyammonium sulfone chloride inhibitors (2) (4) (6) (8) (ll) (l3) (l5) (l6) (I9) (20) (22) (comparative example) Concentration 5O 50 5O 50 5O 5O 50 50 I 50 5O 50 (ppm) I Corrosion inhibitor efficiency 9L4 9 l .5 92.4 94.] 90.8 88.6 89.4 93.5 94.6 91.5 92.0 62.5

Test panel: Polished mild steel plate (5. GJI-ll-SPCCB X 20 X 1 mm). Corrosive liquid: City water Amount of liquid: 5 cc per cm of the steel plate Treatment: At 50C 2C for hours with agitation Table 3 Compara- Compara- Corrosion tive tive Polyinhibitors inhibitor inhibitor sulfone d l Concentra- I I tion l0 l0 2 l0 5 l0 *l0 5 a l0 l0 l0 5 (p Corrosion r inhibitor 82.4 2 5 91.5 92.6,: 90.4 92.4 94.5 98.4 99.1 96.2 93.5 98.4 efficiency Corrosion Polyinhibitors sulfone Concentration 5 l0 l0 l0 5 2 5 5 5 5 2 (ppm) Corrosion inhibitor 98.4 90.6 94.5 98.2 94.5 93.5 94.4 92.8 93.9 96.4 95.8 efficiency i *Comparative inhibitor (A) was a homopolymer of dimetliyldiallylammonium chloride having the formula:

N----------cl- CH; CH

Comparative inhibitor (B) was dodecyltrimethylammonium chloride.

Test panel: Polished mild steel plate (JIS. G3l4l-SPCCB, 80 X 20 X 1 mm). Corrosive liquid: 10 71 hydrochloric acid.

Amount of liquid: 5 cc per cm of the steel plate.

Treatment: At 20C for I00 hours.

17v EXAMPLE 4 The same test panel as in Example 3 was subjected to corrosion treatment in 10 hydrochloric acid at 50C for 2 hours to examine the corrosion inhibiting effect of polysulfones. The results are shown in Table 4.

ment with hydrochloric acid and sulfuric acid under the following conditions:

Table 4 Compara- Compara- Corrosion tive tive Polyinhibitors sample sample sulfone (2) (1 (ll) (l6) Concentration 10 IO 10 l0 l0 5 l0 l0 l0 5 (ppm) Corrosion inhibitor 78.6 53.1 86.5 84.8 87.8 89.6 94.6 98.9 96.6 94.8 96.5 98.l efficiency (7L Poly- Corrosion sulfone H H U y H ,1 H H H H r: inhibitors (l7) (l8) (I9) (Zl) (24) (26) (27) (28) (29) (3O) Concentra tion 5 IO 10 IO l0 l0 5 l0 5 5 5 (ppm) Corrosion inhibitor' 96.9 98 6 96.5 98.2 94.6 95.4 94.6 93.l 94.2 95.6 96.4 efficiency (7c The same sample as in Table 3.

The same sample as in Table 3.

Test panel: The same test panel as in Table 3. Corrosive liquid: ll) /1 hydrochloric acid. Amount of liquid: 5 cc per mm of the steel plate. Treatment: At C for 2 hours.

' EXAMPLE 5 The same test panel as in Example'l was subjected to corrosion treatment in 10 sulfuric acid at 20C for 100 hours to examine the corrosion inhibiting effect of 25 sulfuric acid 5 ferrous ion (added as ferrous sulfate) at 98 i 1Cfor 3 minutes.

8 hydrochloric acid 7 ferrous ion (added as ferrous chloride) at i 1C for 3 minutes.

Amount of liquid: 350 g of the acid per 2 test panels.

polysulfones. The results are shown in Table 5- The results are shown in Table 6, wherein the descal- Table 5 Corrosion Poy H H H H I, H H H 1, inhibitors sulfone Concentration 100 lo 50 I00 50 2O 20 50 5O 50 (p Corrosion inhibitor 84.5 91.4 86.5 92 5 96.5 92.4 94.6 93.7 89.6 86.5 87.2 efficiency Dodecyl- Polytrimethyl- Corrosion Sulfone 'f Y ammonium inhibitors (l6) (l7) (I7) (20) (20) (21) (23) (25) (26) (27) (28) chloride (comparative example) Concentration 100 20 50 20 50 20. 2O 5O 50 50 50 I00 (ppm) Corrosion inhibitor 96.5 89.5 94.2 86.5 96.4 94.5 96.2 94.5 93.6 96.8 96.8 49.6 efficiency Test panel: Same as in Table 3 Corroshi liquidrlO 9i sulfuric acid M Amount of liquid: 5 cc per cm of the steel plate Treatment: At 20C for I00 hours ing speed is expressed by the time required for the complete removal of mill scale on the surface of metal.

Table 6 Pickling Concentra- Corrosion Pickling Concentra- Corrosion Corrosion liquid and tion of inhibitor Descaling liquid and tion of inhibitor Descaling inhibitors pickling inhibitor efficiency speed pickling inhibitor efficiency speed condition (ppm) (7r) (second) conditions (ppm) (71 (second) None 32 29 Polysulfone l 20 84.5 32 2 20 82.5 32 3 90 86.5 34 4 90 84.2 34 5 90 89.5 38 20 84.2 32 7 25 9E H. .SO 90 90.4 39 8 7r HCl 20 84.4 33 8 5 "2 Fe 40 78.6 33 7 71 Fe" 5 81.0 30 98 i 1C 90 90.5 39 85 1C 20 85.2 33 I 3 minutes 90 83.6 35 mlnutes 30 l I 90 85.2 35 30 86.3 34 I2 40 76.5 32 lO- 80.6 32 I3 90 77.4 32 20 82.2 3] I4 90 88.5 38 20 84.6 3] I6 40 90.0 40 8| .5 3?. I7 60 9L6 40 82.5 3l l8 )0 92.0 4l 20 83.6 32 l9 T? H SO 90 9L2 40 8 Ci HCl 841 33 20 5 "2 Fe 90 90.8 39 7 Q Fe" 20 86.2 33 25 98 I l(.- 90 79.6 36 $5 I lC 30 301 31 26 3 minutes 90 89.6 37 5 minutes 20 84.2 32 27 90 92.1 20 87.6 34 28 90 86.8 35 20 83.6 32 29 82.8 36 10 79.4 3| 30 80 83.5 34 20 86.4 34 Dodeeyltrimethylammonium chloride 100 45.3 42 30 40. 36 (comparative example) EXAMPLE 7 l to IR carbon atoms. aryls having 6 to 24 carbon Copper wires which had discolored to brown in the 35 uwms aralkyls having 7 to 25 carbon atoms carboxy' air were dipped in a 1 7r aqueous solution of hydrochloric acid containing 100 ppm of polysulfone (8) or (27) at C for 30 seconds. and then rinsed with water. Thereafter. the thus treated wires were allowed to stand at 30C and at a relative humidity of lOO '/c. The copper wire treated with hydrochloric acid containing polysulfone (8) showed no change for 3 days and the copper wire treated with hydrochloric acid containing polysulfone (27) showed no change for 5 days. On the other hand. a copper wire which was treated with l 7r hydrochloric acid aqueous solution containing no polysulfone in the same manner as mentioned above was discolored to brown after the lapse of 2 hours.

What is claimed is:

l. A method for inhibiting the corrosion of a metal which comprises adding to a corrosive medium with which the metal comes into contact a corrosioninhibitorily effective amount of a metal corrosion inhibitor represented by the general formula II I S M ](L a l a wherein M is one member selected from the group consisting of methyl. carboxyethyl. cyanomethyl. 2-cyanoethyl. 2- sulfoethyl. sulfopropyl. Z-hydroxyethyl, 3-chloro-2- hydroxypropyl. allyl propargyl or aor B-naphthomethyl; and X is Cl. Br, I, HCOO, CH COO, H- PO HSO H50 CH SO wherein X is the same as defined above and Y is CH; or O: a is an average molar fraction of the S0 component in the general formula and ranges from 0.1 to 0.5; and n is a degree of polymerization.

2. A method according to claim 1. wherein the corrosive medium is water. an aqueous salt solution or an inorganic or organic acid.

corrosion inhibitor is added in an amount of at least 5 ppm to the corrosive medium.

6. A method according to claim 5, wherein the corrosive medium is water, an aqueous Salt solution or an inorganic or organic acid. 

1. A METHOD FOR INHIBITING THE CORROSION OF A METAL WHICH COMPRISES ADDING TO A CORROSIVE MEDIUM WITH WHICH THE METAL COMES INTO CONTACT A CORROSION-INHIBITORILY EFFECTIVE AMOUNT OF A METAL CORROSION INHIBITOR REPRESENTED BY THE GENERAL FORMULA
 2. A method according to claim 1, wherein the corrosive medium is water, an aqueous salt solution or an inorganic or organic acid.
 3. A method according to claim 1, wherein the metal corrosion inhibitor is added in an amount of at least 1 ppm to the corrosive medium.
 4. A method according to claim 3, wherein the corrosive meium is water, an aqueous salt solution of an inorganic or organic acid.
 5. A method according to claim 1, wherein the metal corrosion inhibitor is added in an amount of at least 5 ppm to the corrosive medium.
 6. A method according to claim 5, wherein the corrosive medium is water, an aqueous salt solution or an inorganic or organic acid. 